The present invention relates to a video recording apparatus, particularly a portable video recording apparatus, which picks up an image of a subject, generates an electrical signal corresponding to the image of the subject, and records the electrical signal on a magnetic tape.
A typical example of such a video recording apparatus is an integrated or all-in one camera/VTR.
FIG. 8 shows an example of a conventional all-in-one camera/VTR. As illustrated, it comprises a system control section 1, a power supply section 2 for supplying electric power to various circuits, an image pickup section 3 for picking up the image of a subject and generating an electrical video signal corresponding to the subject thus picked up, and a magnetic recording/reproducing section (hereinafter referred to as VTR section) 4 of a rotary head type which records the video signal outputted from the image pickup section 3 on a magnetic tape, and reproducing the recorded video signal.
The image pickup section 3 comprises an image pickup device 5, an electrical signal processing circuit 6 and a synchronous signal generating circuit 7. To pick up a subject, an image of the subject is formed on a charge storage section of an image pickup element, such as a CCD (charge coupled device) in the image pickup device 5 by means of lenses. The image of the subject formed in the charge storage section is scanned by a signal from the synchronous signal generating circuit 7 and read out to be an electrical signal continuous in time. The electrical signal is then converted at the electrical signal processing circuit 6 into an ordinary television signal and this television signal is then outputted from the image pickup section 3.
The VTR section 4 comprises a video signal recording circuit 8, a video signal reproducing circuit 9, a drum rotation control circuit 12, and a tape travel control circuit 13. The television signal outputted from the image pickup section 3 is converted at the video signal recording circuit 8 into an FM (frequency-modulaled) signal, and then supplied through a recording/reproducing switch 10 and a rotary transformer, not shown, to a rotary magnetic head 11, and is then recorded by the rotary magnetic head 11 on the magnetic tape.
The drum rotation control circuit 12 comprises a phase comparator 21, a phase compensation circuit 14, a speed control circuit 15, a motor drive circuit 16, a drum motor 18, a drum rotary position detecting device 17 for detecting the rotary position of the rotary drum, and a speed detecting device 19 for detecting the rotational speed of the drum motor 18. The control of the rotation of the rotary drum is conducted in the following manner.
The rotary position detection signal, i.e., the so-called PG signal from the drum rotary position detecting device 17 is phase-compared at the phase comparator 21, either with a vertical synchronous signal outputted from the image pickup section 3 when a video signal is recorded on a magnetic tape, or with a reference signal from an internal reference signal generating circuit 22 when recording of a video signal on a magnetic tape is not made. The phase error signal outputted from the phase comparator 21 is supplied to the phase compensation circuit 14 which performs phase compensation. The speed detection signal from the speed detecting device 19 is supplied to the speed control circuit 15, which produces a speed error signal, which is added to the output of the phase compensation circuit 14, and the sum signal is inputted to the motor drive circuit 16. The motor drive circuit 16 thereby drives the drum motor 18 to control the rotary phase of the rotary drum.
The system control section 1 performs control over the entire system, and is connected to receive signals or information from a start/stop switch 40, a standby switch 41, various other switches, collectively indicated by reference numeral 44, and various sensors 42, and produces various power supply control signals and various system control signals, to bring the system into a certain operating state and to cause various display devices 43 to perform display or indication.
The power supply section 2 supplies electric power to various circuits in accordance with the various power control signals from the system control section 1.
An electronic viewfinder 45 has a built-in CRT on which a reproduced signal from the video signal reproducing circuit 9 is displayed during the signal reproduction, while the television signal from the electrical signal processing circuit 6 is displayed in any other operating state.
Now, transitions between the various system operating states according to the conventional system will be described with reference to FIG. 9.
In FIG. 9, EJECT represents the state in which a cassette is inserted or taken out. STOP represents the state of waiting or standby. F.multidot.F represents the state of fast forward travel of the tape. REW represents the state of rewinding or reverse fast travel of the tape. P.multidot.B represents the state of reproduction of the signal recorded on the tape F.multidot.S and R.multidot.S respectively represent the state of speed search with forward and reverse travel. REC represents the state of recording the subject picked up on the tape. REC PAUSE represents the state of waiting or pause before transfer to the REC state. POWER represents the state of "power off".
In this conventional system, the so-called loading standby system is adopted, by which upon insertion of a cassette, the tape is loaded and wound around the rotary drum, and, with such conditions, the system becomes in the state "STOP" of standby. In the STOP state, no power is supplied to all the circuit blocks except the system control section 1. To pick up the subject, a specific key is pressed, so that the operating state of the system is transferred into REC PAUSE, a state of pause ready for recording. In this state, electric power is supplied at least to the system control section 1, the image pickup section 3, the electronic viewfinder 45, and the drum rotation control circuit 12 within the recording/reproducing section 4 required for rotating the rotary drum. If the start/stop switch 40 is pressed in the state of REC PAUSE, supply of electric power to the circuit block required for recording the signal is commenced, and the tape travel is commenced and the signal picked up by the pickup section 5 is recorded on the tape (REC state). If the start/stop switch 40 is pressed in this REC state, the system is transferred again to the REC PAUSE. To begin reproduction from the STOP state, a manual key for the reproduction may be manipulated, upon which an electric power is supplied to the system control section 1, electronic viewfinder 45 and the circuit blocks within the recording/reproducing section 4 required for the signal reproduction (PB state).
FIG. 10 shows transition between operating states in another conventional system. This system is intended to simplify the manipulation, and the state of REC PAUSE and the state of STOP in FIG. 9 have been made one and the same. In this example, the STOP state is always a state of pause ready for recording. The recording of the picked-up image can be started and terminated simply by manipulating the start/stop switch 40.
The reason why the state of pause ready for recording is necessary in conventional all-in-one camera/VTRs, i. e, why the conventional all-in-one camera/VTR must assume the state of pause ready for recording before entering the state of recording is given below. With an all-in-one camera/VTR as well as other video/audio recording apparatus, it is desired that the recording should begin immediately when a manipulation switch is manipulated. This is mainly because of the psycological demand of the operator. Such a requirement is particularly severe with an all-in-one camera/VTR. The time from the manipulation of the start/stop switch until the commencement of the actual recording in commercially available all-in-one camera/VTR is usually about one to two seconds, and such time delay is considered to be acceptable.
The manipulation and the operation of the VTR at the time of "shooting" will be described.
To shoot, the lens is directed to the subject to be shot, and the image of the subject is confirmed by means of a viewfinder, and the focus is adjusted manually or automatically. After these preparatory operations, a manipulation key such as the start/stop switch 40 is manipulated to provide the all-in-one camera/VTR with the information that the recording should be started. Upon the delivery of such information, the travel of the magnetic tape is started. When the travel of the tape is started the signal already recorded on the tape is reproduced, and the travel of the tape is so controlled that the scanning locus followed by the magnetic head mounted on the rotary drum conform to the locus of the track of the signal already recorded on the tape. This is to ensure continuity with the previous recording. When the scanning locus of the magnetic head is brought into conformity with the track already recorded, actual recording on the tape is started.
As has been described, the conventional system of FIG. 8 requires various manipulations and operation for implementing the recording. The state of pause ready for recording, i. e., REC PAUSE state of FIG. 9 or STOP (REC PAUSE) state of FIG. 10, is provided so that during this state, electric power is supplied to the image pickup section 3, the electronic viewfinder 45 and the drum rotation control circuit 12, to enable confirmation of the image of the subject inputted through the lens on the screen of the electronic viewfinder 45, and to cause rotation of the rotary drum in such a manner that the rotational phase of the rotary drum is in phase with the sweeping (scanning) of the charge storage section in the image pickup section 5 for storing the image of the subject. Accordingly, if, in the state of pause ready for recording, the start/stop switch 40 is manipulated, the time (about 1 to 2 seconds) necessary for bringing the locus of the head into conformity with the locus of the previous track is taken before the recording is actually started.
The conventional all-in-one camera/VTRs are usually portable and a battery is used as a power supply when the all-in-one camera/VTR is used outdoors. The power consumption of these all-in-one camera/VTRs during shooting is about 6 to 10W, and it is usually so set that the shooting time of about 1 hour is guaranteed, taking account of the suitable size and weight of the battery.
When the system is in the state of pause ready for recording, as at REC PAUSE in FIG. 9 or STOP (REC PAUSE) in FIG. 10, it is necessary that the electric power be supplied to most of the circuits, and the power consumption during such a state is 80% with respect to the power consumption during shooting and recording. If the state of pause ready for recording is continued for a long time, the consumption of the battery is large. This will shorten the time of actual recording.
Various arrangements are employed to reduce the power consumption when the actual recording is not made. As an example, when the pause state continues 3 to 5 minutes, the system is automatically transferred to a standby state in which electric power is supplied only to those circuits within the system control section 1 required to recognize the operating state. In such a standby state, the power consumption is not more than about 1W. When the standby switch 41 is manipulated during the standby state, the system is returned to the pause state. The same standby switch 41 can also be used for transfer of the system to the standby state.
As was described, the power consumption of the conventional all-in-one camera/VTR during the recording pause state is large. Even if a standby switch is provided, the consumption of the battery during actual use is large. Moreover, the provision of the standby switch makes the manipulation complicated.
Furthermore, when the recording is to be resumed by terminating the standby state, the drum has been at a stop, and has been out of synchronism with the video signal (synchronous signal) from the image pickup section 3, and the drum has a large inertia and hence is difficult to follow the speed control. Accordingly, the drum is not brought into phase with the video signal and no recording of the signal is made until elapse of about 4 to 5 seconds after the standby state is terminated.